The present invention relates to the art of reclosable sacks or bags of fusible material, and is more particularly concerned with an improved reclosable bag having a separate top closure that is affixed to a tubular bag body.
Reclosable bags and thermoplastic material are well known in the art. For instance, the patent to Sullivan, et al., U.S. Pat. No. 4,637,063, assigned to the Assignee of the present invention, describes a bag structure having a primary and secondary closure for access to the contents within the bag. The primary closure is non-reclosable, while the secondary closure comprises a reclosable fastener zipper for selectively opening and closing the bag top opening. The Sullivan reference describes a bag structure having an inner thermoplastic liner which is heat-sealed at the inner surface to form the primary closure. The bag structure includes an outer body that is composed of a paper material.
A similar multi-layer bag is shown in the Goodrich patent, U.S. Pat. No. 3,958,749. The Goodrich bag includes an inner bag of a fusible material enclosed within an outer bag of a multi-layer paper or other non-fusible material.
Several bag structures in the art have combined a primary non-reclosable closure with a secondary reclosable closure. The primary non-reclosable closure provides a tamper-evident or security feature to the bag, while the reclosable closure provides means to selectively open and close the bag when the primary closure is removed. In one approach, as embodied in the patent to Ferrell, U.S. Pat. No. 4,241,865, owned by the present Assignee, a reclosable shipping sack is disclosed having an outboard reclosable fastener and an inboard stitched fastener. However, the sewn closure inboard of the reclosable closure is undesirable in applications which require that the bag be moisture-proof. The perforations left by the stitched fastener permit leakage through the bag wall. Another problem, particularly with thermoplastic bag walls, is a tendency to tear along the perforations left by the stitched fastener.
In order to avoid the problem of inboard stitched fasteners, the non-reclosable closure has been positioned outboard the reclosable closure. In this instance, the top closure includes some portion that is affixed to the outer wall of the tubular bag body. When the closure is formed from a thermoplastic material, the primary and secondary closures are frequently integrally formed in a single extrusion process. The use of heated pressure bars to seal the thermoplastic closure to the bag body is well known in the art. It is frequently desirable to adhere the top closure to the outer surface of the thermoplastic bag body without likewise adhering the inner surfaces of the mouth of the body together. In the past, a heat-resistant plate has been situated between the inner layers while the heated pressure bars are applied to the top closure and bag outer surface. One example is shown in the patent to Arai, U.S. Pat. No. 3,839,128, which discloses an apparatus for manufacturing containers from thermoplastic film in which a stationary guide is placed between inner layers of thermoplastic film that are not intended to be heat-sealed together.
No prior art reference is known to applicant in which a thermoplastic top closure is heat-sealed to the outer wall of a thermoplastic bag body in which the inner wall of the bag body is not similarly heat sealed. Present bag structures avoid this type of fusible construction entirely or employ a heat resistant plate between inner surfaces to keep the top opening of the bag body from being inadvertently closed when the top closure is attached.